How this calculator works
Estimate paintable wall area, subtract large openings where appropriate, then account for coverage and coats. The result is an estimate and may vary with the product, site conditions, measurement accuracy and installation method.
Before you use the estimate
- Measure the area carefully and keep units consistent.
- Review any waste allowance and material coverage assumptions.
- Check the product packaging or supplier specifications before purchasing.
Worked example
Frequently asked questions
How much paint do I need for a 12×12 room?
Roughly 1.5 gallons per coat for the walls (about 480 sq ft of wall area at 350 sq ft per gallon). Enter your exact dimensions above and choose 2 coats for full coverage. New to this? Our room measuring guide shows how to get those dimensions right.
How much area does one gallon of paint cover?
About 350 square feet per coat on smooth walls — less on textured or unprimed surfaces. Adjust the coverage field above to match your paint.
Should I apply one coat or two?
Two coats gives true color and durability, especially over dark colors or new drywall. The calculator shows the difference.
How much paint do I need for a house exterior?
Measure each wall’s length × height, subtract windows and doors, and enter the total area above. Most exteriors need two coats — the calculator prices one and two coats.
Does a ceiling need more paint than walls?
Often yes — texture and overhead rolling use more paint. Figure 300–350 sq ft per gallon for ceilings, or lower the coverage field above to be safe.